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How To: LE5 Fuel Return System Ver 2 (no welding required)

I want to start by saying this thread is inspired by the following thread written by @slvrsky07

https://www.skyroadster.com/forums/f2...-system-40748/

I am not replacing his thread since it is a very good thread. For the fuel pump assembly removal, connecting the return line to the assembly and tuning, refer to his post as there is nothing really I'm going to add here except pictures of how I did exactly what he talks about in that thread.

The main difference between his thread and mine is the fuel rail and regulator setup in the engine bay. slvrsky07 used a factory fuel rail, welded on a AN bung, and remotely mounted the regulator. This works great IF you can weld. I can't. So I went with another solution. I decided to use the DDM center feed fuel rail rather than a modified stock fuel rail. His way is probably substantially cheaper if you feel comfortable welding the stock rail. Here is the layout of the system I built:



A quick note on braided line and AN fittings. There are a number of types of braided line but they come down to two styles, Rubber and Teflon (also called PTFE). The rubber line is fine for gasoline but if you want to run E85, you need the Teflon/PTFE. The type of braided line you choose will determine which fittings you need for that line. If you use rubber, be sure the hose end fittings you get are for rubber braided line. If you get the Teflon hose, be sure the hose end fittings are for Teflon line. Visually the hose fittings for Teflon are flared where they go on the line.

Rubber:


PTFE (note the flared fitting at the top of the picture compared to the above image):


I chose the Teflon hose just in case I would like to use a E45 or E85 blend in the future.

DDM's fuel rail is set up to be used for a return system if you call up Dave and special order the rail. However, you need to know what you're ordering. The DDM fuel rail usually has a 3/8" NPT male plug in each end of the rail and then a braided fuel line with a -6 AN 90 degree fitting screwing into a -6 AN male to male fitting in the top center of the rail. You want to order it with none of those installed. You just want the rail and the two metal tabs that are mounted to it that will attach the rail to the engine's cylinder head. If you want, you can have Dave install a Male 3/8" NPT to Male -6 AN fitting on the front of the rail and a Male 3/8" NPT to Female -6 AN fitting in the rail and then make a braided line about 12" long with a 180 degree hose end with a -6 AN Female fitting on one end and a 90 degree hose end with a -6 AN Female fitting on the other. You'll also need a -6 AN plug with o-ring to plug up the port for the center feed line DDM normally uses.

@[email protected], if this is something you want to offer, we can get together and I can go over the fittings and dimensions for what someone would need. Actually, this whole system could be an entire kit you could offer without much trouble.

If you just get the rail, you will need to treat the NPT threads with some type of thread sealant (tape or liquid work...I didn't have great luck with the liquid though) and assemble them into each end of the rail. You want the one with the -6 AN Male end on the end of the rail that is towards the front of the car and the one with the -6 AN female fitting on the end of the rail that will face the rear of the car. Install the -6 AN plug with a fuel safe O-ring installed to prevent leaking. If you use liquid thread sealant, be sure to let it cure overnight before installation.

Once the rail is prepared, you need to attach the regulator. I used a Fuelab 515 Series regulator. You can get them on eBay for around $160 and they come in a bunch of different colors.



These regulators have three -6AN ports. The two on the sides are your inputs and the one on the bottom is for the return line. You'll need to plug one of the end input ports as you will only need one. The one you plug will face the rear of the car. In the other two ports, you will want to install -6 AN Male to Male port fittings and install O-rings on the side of the fitting you're inserting into the regulator.

In addition to the regulator, you'll need a -6 AN Male to Female fitting with a 1/8" NPT port for a fuel pressure gauge fitting in the side of it. Again, these are pretty easy to get on eBay and look like this:


You can get these with a gauge but I picked up a Marshall brand gauge since the one that came with mine from eBay didn't work. When you install the gauge into the fitting, be sure to use thread sealant (tape or liquid) to prevent leaks.

Now the FueLab regulators come with a gauge port so it may seem unnecessary to install this gauge fitting. The reason I installed it like this was because I do not believe the regulator will clear the various engine components if you don't have this "spacer" of the fuel pressure fitting.

With these parts, you're ready to assemble the regulator end of the rail. Install the male end of the fuel pressure gauge AN fitting into the female AN fitting on the rear or the rail. Position it so that the gauge face is parallel to the top of the DDM fuel rail (this will put it at about a 45 degree angle towards the driver's side of the car when installed). Now attach the regulator to the fuel pressure fitting using the male AN fitting that is in the side port of the regulator. You want to put the regulator on it's side with the three mounting holes for the mounting bracket facing up. Finally, attach a 90 degree -6 AN male to female fitting to the -6 AN male fitting that is in the return port on the regulator. This 90 degree fitting should face down. You don't want it facing straight down though as it needs to clear the camshaft position sensor plug on the back side of the engine. Angle it about 20 degrees from straight up and down away from the rear of the rail. (It should angle back towards the rear of the car slightly.)

With this layout, you should have a pretty solid mount on the fuel regulator but I wanted to add a bit of support so I fabricated a metal mount for it. I got some sheet metal from Lowes and used a dremel tool to cut out the pattern. If you've never done something like this before, use a piece of cardboard to cut out a template. You can easily cut and bend the cardboard to get the angles and dimensions right. Once you have a template, transfer the pattern to the sheet metal and cut out your design. There are three good bends in the design I used. I just put the flat metal in a vice along the line where I wanted to bend it then used a hammer to make the bend. Worked like a charm.

To mount it, I used the three provided holes and screws in the regulator for the mount to regulator attachment. For the rail, I removed the two screws that hold the rear mounting bracket to the rail and made matching holes in the mount. To attach the mount, I first put the DDM bracket on the rail, then the washers that were on the screws on the bracket. Then the mounting bracket goes on top of the washers and DDM bracket, then another washer. Then the DDM mounting screw goes back in through the washer, regulator bracket, another washer, the DDM bracket and finally into the rail. The reason I put a washer between the new bracket and the DMM bracket was because the DDM bracket sat slightly below the surface of the DDM rail. By placing the washer between the two brackets allows the top bracket to sit flush with the top of the rail without there being a gap between the two brackets.

Here are some pictures of the mount attached to the rail and regulator. As noted, ignore the extra fittings on the return port of the regulator. This was for my original idea that just didn't work because the fittings hit items on the back side of the engine bay when installed.







This completes the assembly of the fuel rail. After you transfer your injectors to the new rail, you can put the rail in the car. The return line should be routed under the car by this point and should come up in the rear portion of the engine bay. You should be able to attach it to the return port fitting on the regulator at this point before maneuvering the rail into position. Just be sure that you route it up to the rail in a way where the vacuum lines in the engine bay won't stop you from getting the rail in position. You want to start to install the rail by maneuvering the regulator in under the vacuum lines that are in the rear of the engine. Once you get the regulator side under those lines, you want to push the rail back to allow the front of the rail to get under the coolant overflow line where it attaches to the head at the front of the engine.

Now you can attach the fuel line's 180 degree AN fitting end to the front of the fuel rail and plug in the quick connect male fitting into the stock fuel line.

At this point, leave the vacuum line for the regulator off and start the car.

First thing you want to do is check for leaks and address those. I primed the system without starting the car and saw no leaks but then saw a number of them after starting it so don't believe just priming it is enough to check for leaks. Also, let it run for a couple minutes because some leaks take a bit of time to develop.

Once you know there are no leaks, set your fuel pressure. The adjustment for the regulator will be under the window sill but should be easily accessible for adjustment. Here is a picture of it under the window sill once installed.



Once you have the pressure adjusted, turn off the car and attach the vacuum line for the boost reference to something that ties into your intake manifold.

NOTE that since this system is really unnecessary for a NA 2.4, it is assumed you're boosted in some form or fashion. I used the same line that I used for my turbo bypass valve to run the regulator too. Here is a picture of the rail installed with my new fuel pressure gauge:



For those wondering, I can still get to my oil filter cap for oil changes with the oil filter socket and an extension just like I could before this modification. Being able to do an oil change without taking out the whole fuel rail was important.
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V.A.L. (#1108)
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Max (#1547)
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Last edited by Robotech; 03-20-2017 at 02:35 PM.
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